Radioactive seed with multiple markers and method for using same

ABSTRACT

A radioactive seed which discloses the orientation and the location of the seed when the seed is exposed to X-ray photography is provided. The seed contains multiple X-ray detectable markers which will disclose the orientation and the location of the seed when the seed is exposed to X-ray photography. The seed can also have a single marker which wraps around the external surface of the seed or wraps around a carrier body within the seed. The single marker will also disclose the orientation as well as the location of the seed.

This application is a continuation-in-part application of applicationSer. No. 08/904,695, filed Aug. 1, 1997 now abandoned.

FIELD OF THE INVENTION

This invention relates to radioactive seeds and, in particularembodiments, to improved radioactive seeds for treating diseased tissueswith radiation therapy.

BACKGROUND OF THE INVENTION

Over the years, brachytherapy sources implanted into the human body havebecome a very effective tool in radiation therapy for treating diseasedtissues, especially cancerous tissues. The brachytherapy sources arealso known as radioactive seeds in the industry. Typically, theseradioactive seeds are inserted directly into the tissues to beirradiated using surgical methods or minimally invasive techniques suchas hypodermic needles. These radioactive seeds typically contain aradioactive material such as iodine-125 which emits low energy X-rays toirradiate and destroy malignant tissues without causing excessive damageto the surrounding healthy tissue, as disclosed by Lawrence in U.S. Pat.No. 3,351,049 ('049 patent). Because radioactive materials likeiodine-125 have a short half-life and emit low energy X-rays, theradioactive seeds can be left in human tissue indefinitely without theneed for surgical removal. However, although radioactive seeds do nothave to be removed from the embedded tissues, it is necessary todetermine the position and the number of radioactive seeds implanted ina patient's tissue to effectively treat the patient. This information isalso useful in computing the radiation dosage distribution in the tissuebeing treated so that effective treatment can be administered.

In the '049 patent, the radioactive seed includes a therapeutic amountof radioisotope appropriately distributed on a carrier body. The carrierbody is sealed inside an elongated cavity of a capsule to prevent theradioisotope from interacting with body fluids while at the same timepermitting the radiation to pass through the walls of the capsule.Furthermore, to allow X-ray detection of the radioactive seed, theradioactive seed contains an X-ray marker made of a dense, high atomicnumber material, such as gold, which can block the transmission ofX-rays so that the radioactive seed can be detected by using X-rayphotographic techniques. The capsule, which is typically made out of alow atomic number material, cannot be detected using X-ray photographictechniques because low atomic number materials allow X-rays andradiation to pass through them, instead of blocking X-rays andradiation.

The '049 patent discloses two methods of providing an X-ray marker. Inone method, a small ball constructed of a dense, high atomic numbermaterial, such as gold or tungsten, is provided in between twocylindrical carrier bodies impregnated with a radioisotope. In anothermethod, a wire made of a high atomic number dense material is locatedalong the central axis of symmetry of the carrier body that isimpregnated with a radioisotope. Both the X-ray marker and the carrierbody are encapsulated and sealed within a low atomic numbered materialcontainer or a capsule which minimally absorbs the radiation emitted bythe radioisotope.

Although the above-described methods of providing an X-ray marker areeffective in detecting the radioactive seed, they have certain problems.In the first method in which a small ball is provided as a X-ray marker,the ball just appears as a circular dot on an X-ray film and does notprovide any information as to the orientation of the radioactive seed.Since the orientation of the radioactive seed is not known, theradiation dosage distribution cannot be computed accurately. In thesecond method in which a centrally located wire is provided as an X-raymarker, the orientation of the radioactive seed can be determined.However, the second method presents manufacturing problems, such aspositioning the wire centrally at the axis of symmetry, which can raisethe cost of manufacturing the radioactive seeds.

In other radioactive seeds such as one disclosed by Kubiatowicz in U.S.Pat. No. 4,323,055 ('055 patent), a long cylindrical rod-like memberlocated centrally within the seed is usually employed as an X-raymarker. In the '055 patent, a silver rod coated with iodine-125 isemployed as an X-ray marker. Although such X-ray markers like the silverrod in the '055 patent may disclose the orientation of the seed, thesilver rod in the '055 patent is coated with the iodine-125 byperforming a complicated chemical process which in turn will complicatethe overall manufacturing process and raise the cost of manufacturing.As discussed above, the orientation of the seed can be very important incomputing the radiation dosage distribution. Therefore, simpler and morecost effective apparatuses and methods are needed in providing X-raymarkers which will disclose the orientation of the radioactive seed whenthe seed is exposed to X-ray photography.

SUMMARY OF THE DISCLOSURE

It is an object of an embodiment of the present invention to provide animproved radioactive seed for use in radiation therapy, which obviatesfor practical purposes, the above-mentioned limitations.

It is also an object of an embodiment of the present invention toprovide a system for monitoring radioactive dosages in affected tissuein brachytherapy.

It is also an object of an embodiment of the present invention toprovide simple and cost effective X-ray detectable markers which willdisclose the orientation of the radioactive seed when the seed isexposed to X-ray photography.

According to an embodiment of the present invention, a radioactive seedfor use in radiation therapy includes a sealed housing having aninternal cavity, at least one carrier body disposed within the cavityfor maintaining and distributing a radioisotope along the length of thecavity and a plurality of X-ray detectable markers distributed among theat least one carrier body such that the distribution of the X-raydetectable markers discloses the orientation of the radioactive seedwhen the seed is exposed to X-ray photography.

In particular embodiments of the present invention, the carrier bodycomprises a plurality of separate carrier units in which each of thecarrier units is impregnated with the radioisotope. The carrier unitsare evenly distributed along the length of the cavity so that the seedemits substantially uniform radiation around the sealed housing of theseed. However, in alternative embodiments, the carrier units can beconcentrated at one end of the seed. In addition, the X-ray detectablemarkers are distributed among the carrier units so that the markers willdisclose the orientation of the seed when the seed is exposed to X-rayphotography. Both the X-ray detectable markers and the carrier unitspreferably have a substantially spherical shape like a ball or a bead sothat the markers and carrier units can be easily rolled into the cavityof the housing during the manufacturing process.

In other embodiments of the present invention, the X-ray detectablemarker wraps around the carrier body or the sealed housing in a spiralshape to reveal the location and the orientation of the radioactiveseed. In other embodiments of the present invention, radioactive seedshave different configurations of X-ray detectable marks for identifyinga particular type of radioactive source in the seed or dosage level.

Other features and advantages of the invention will become apparent fromthe following detailed description, taken in conjunction with theaccompanying drawings which illustrate, by way of example, variousfeatures of embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING

A detailed description of embodiments of the invention will be made withreference to the accompanying drawings, wherein like numerals designatecorresponding parts in the several figures.

FIG. 1a is a cross-sectional view of a radioactive seed in accordancewith a first embodiment of the present invention.

FIG. 1b is a cross-sectional view of a radioactive seed in accordancewith a second embodiment of the present invention.

FIG. 2 is a cross-sectional view of a radioactive seed in accordancewith a third embodiment of the present invention.

FIG. 3a is a cross-sectional view of a radioactive seed in accordancewith a fourth embodiment of the present invention.

FIG. 3b is a cross-sectional view of a radioactive seed in accordancewith a fifth embodiment of the present invention.

FIG. 3c is a cross-sectional view of a radioactive seed in accordancewith a sixth embodiment of the present invention.

FIG. 3d is a cross-sectional view of a radioactive seed in accordancewith a seventh embodiment of the present invention.

FIG. 4 is a side view with a partial cross-sectional view of aradioactive seed in accordance with a eighth embodiment of the presentinvention.

FIG. 5 is a cross-sectional view of a radioactive seed in accordancewith a ninth embodiment of the present invention.

FIG. 6 is a cross-sectional view of a radioactive seed in accordancewith a tenth embodiment of the present invention.

FIGS. 7a through 7 d show cross-sectional views of radioactive seedswith different marker configurations to identify particular radioactivesources and dosage levels within the seeds.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in the drawings for purposes of illustration, the invention isembodied in a radiation seed. In preferred embodiments of the presentinvention, the radiation seed is used in the human body. However, itwill be recognized that further embodiments of the invention may be usedin animals or other applications where radiation and markers arerequired.

Referring to FIG. 1a, a radioactive seed 1 in accordance with a firstembodiment of the present invention includes a tubular container or ahousing 5 with an internal cavity 22 which contains a therapeutic amountof radioisotope 15 evenly distributed on a carrier body 20 along thelength of the cavity 22. In addition, X-ray detectable markers 10 a and10 b are disposed at two ends of the carrier body 20, respectively, andthe housing 5 is sealed at two ends 25 and 26 to prevent theradioisotope 15 from interacting with body fluids while the seed 1 isimplanted within a human tissue.

As shown in FIG. 1, the housing 5 isolates the radioisotope 15 and theX-ray detectable markers 10 a and 10 b from body fluids by completelyencapsulating the radioisotope 15 and the markers 10 a and 1 b.Therefore, the material for the housing 5 needs to be a non-toxicmaterial that will not interact physically or chemically with bodyfluids. Otherwise, the housing 5 needs a coating of non-toxic materialthat will prevent interaction between the housing 5 and body fluids. Inaddition, the housing 5 should be constructed of a material which willnot significantly attenuate the radiation emitted by the radioisotope 15while having sufficient mechanical strength to allow the implantation ofthe seed 1 into the human body using hypodermic needles or otherappropriate instruments. High atomic number material such as gold orplatinum may have sufficient mechanical strength and the requisitenontoxicity, but high atomic number materials like gold will absorb andattenuate a significant amount of radiation emitted by the radioisotope15 so that effective treatment cannot be administered to a patient.Thus, high atomic number material is not a suitable material for thehousing. However, low number atomic metal such as stainless steel ortitanium has the requisite nontoxicity, sufficient mechanical strengthand the requisite minimal absorption characteristic to preventsignificant attenuation of the radiation emitted by the radioisotope 15.In alternative embodiments, medical grade plastics, ceramics, or thelike may be used.

Titanium has a high strength-to-weight ratio and a low atomic number, inaddition to being exceptionally corrosion resistant and non-toxic. Thus,titanium is a very suitable material for the housing 5. The wallthickness of the titanium may vary from 0.001 of an inch to 0.005 of aninch while the attenuation is about 5-7% per thousandths of an inch forlow energy X-rays, such as from iodine-125 or palladium-103, and wouldbe lower for higher energy photons. An optimum value of wall thicknessis approximately 0.002 inch. However, smaller or larger thicknesses maybe used, with the thickness being dependent on the location of use, theamount of radiation and the type of radioactive material. The ends ofthe titanium housing can be sealed by using various techniques known inthe industry such as laser welding or the like. Such a technique isdescribed in U.S. patent application Ser. No. 09/048,517, entitled“Laser Welded Brachytherapy Source and Method of Making the Same,” filedon Mar. 26, 1998, assigned to North American Scientific, Inc., andincorporated herein by reference. In alternative embodiments, the endsmay be sealed by a cover secured by adhesives or crimping.

The housing 5 should be preferably designed for implantation usinghypodermic needles or other similar instruments designed for implantingthe seed 1. As a result, the housing 5 preferably has a long, thinelongated shape with an outer diameter of about 0.5 to 1 millimeter anda length of about 4-5 millimeters to allow the seed 1 to pass through ahypodermic needle. However, smaller or larger diameters may be used,with the diameter being dependent on the location and application inwhich the seed will be used.

As mentioned above, the housing 5 has an inner cavity 22 which containsa carrier body 20. In preferred embodiments, the carrier body 20 is anion exchange resin material impregnated with the radioisotope 15. Thecarrier body 20 is used to concentrate, collect and support theradioisotope 15 so that the radioisotope 15 can be evenly distributedalong the length of the cavity 22 to prevent having a point source whichcan prevent effective treatment. The carrier body 20 generally conformsto the shape of the inner cavity 22 so that the carrier body 20 can beeasily inserted into the cavity 22 during the manufacturing process. Thecarrier body 20 can be constructed from any suitable material that canbe impregnated with the radioisotope 15 and that can allow evendistribution of the radioisotope 15 along the length of the seed 1.However, the carrier body 20 should be preferably constructed from a lowatomic number material since high atomic number material can absorb theradiation from the radioisotope 15. In alternative embodiments,plastics, ceramics, composites, low atomic number metals and the likemay be used as carrier bodies.

In preferred embodiments, the material for the radioisotope 15 should bechosen from a material which has a radiation energy in the soft X-rayregion, from about 20 to 100 Kev and a half-life of about 5 to 100 days.If the material has a half-life shorter than 5 days, then the materialwill tend to dissipate before it can be packaged and shipped, and if thematerial has a half-life longer than 100 days, then the radioactive seedmay have to be removed surgically since the seed may emit radiation evenafter the treatment period is over. Materials such as iodine-125 orpalladium-103 can serve as a suitable radioisotope material for theradioisotope 15 since both iodine-125 and palladium-103 have a radiationof approximately 30 Kev energy X-rays and possess a half-life of about60 days and a half-life of about 10 days, respectively. However, inalternative embodiments, other materials and half-lives may be used,with them being dependent on the treatment period, the radiationintensity needed and the location where the seed 1 will be placed.

In addition to having the carrier body 20 impregnated with radioisotope15, the cavity 22 also contains a plurality of X-ray detectable markers10 a and 10 b. The X-ray detectable markers 10 a and 10 b are eachdisposed adjacent to the two ends of the carrier body 20, respectively.However, instead of using just two X-ray detectable markers, more thantwo X-ray detectable markers may be used. By having two or more X-raydetectable markers, the orientation of the seed 1 can be detected, aswell as the location of the seed 1, when the seed 1 is exposed to X-rayphotography. Since the X-ray detectable markers 10 a and 10 b reveal twoends of the seed 1, the orientation of the seed 1 can be determinedbased upon the locations of the X-ray detectable markers 10 a and 10 b.In other words, the orientation of the seed 1 can be determined from aline intersecting the X-ray detectable markers 10 a and 10 b. Bydisclosing the orientation of the seed 1 in addition to its location,the preferred embodiments of the present invention may also allow formore accurate determination of the radiation dosage distribution in thetissue being treated so that a more effective treatment can beadministered. As mentioned above, any multiple number of X-raydetectable markers can be employed to disclose the orientation of theseed 1. For example, instead of just having one marker at each end ofthe carrier body 20, two markers can be placed adjacent to each end ofthe carrier body 20.

In preferred embodiments of the present invention, the X-ray detectablemarkers have a substantially spherical shape like a bead or a ball sothat the markers can be easily rolled into the inner cavity 22 tofacilitate the manufacturing process and reduce the manufacturing cost.However, in alternative embodiments, other shapes, such as cylinders orthe like, may be used so long as manufacturing is not impeded. The X-raydetectable markers are preferably constructed from a dense, high atomicnumber material, such as gold or tungsten, which will block thetransmission of X-rays so that the X-ray detectable markers will appearon an X-ray film used in X-ray photography. However, in alternativeembodiments, other materials such as lead or uranium may be used so longas X-rays are blocked and there is no health hazard from their use.

The diameter and the size of the X-ray detectable markers are preferablysufficiently large to allow X-ray detection (i.e., appear on the X-rayfilm), but the markers are preferably appropriately sized so that themarkers would not attenuate the radiation emitted by the radioisotope15. If a large amount of dense, high atomic number material is used asX-ray detectable markers, then the markers would severely attenuate theradiation emitted by the radioisotope and decrease the effectiveness ofthe seed. However, as seen in FIG. 1, the X-ray detectable markers 10 aand 10 b are located at two ends of the seed 1 and would absorb only asmall amount of the radiation emitted by the radioisotope 15. Since thetwo markers 10 a and 10 b are located at two ends of the seed 1, theuniformity of the radiation emitted around the housing 5 of the seed 1is only slightly affected.

FIG. 1b shows a radioactive seed 2 in accordance with a secondembodiment of the present invention. The radioactive seed 2 is similarto the radioactive seed 1 except that the seed 2 has a carrier bodydivided into two separate portions 20 a and 20 b. In addition, the seed2 has another X-ray detectable marker 11 c in between the two portions20 a and 20 b. Therefore, the seed 2 has three X-ray detectable markers11 a, 11 b and 11 c. By having a third marker in the middle, themid-section of the seed 2 can be easily determined, and the seed becomesmore readily identifiable.

FIG. 2 shows a radioactive seed 30 in accordance with a third embodimentof the present invention. A radioactive seed 30 has a housing 40, acavity 47, two ends 48 and 49, and X-ray detectable markers 35 a, 35 band 35 c which are similar to the housing 6, the cavity 21, the two ends23 and 24, and the X-ray detectable markers 11 a, 11 b and 11 c shown inthe embodiment of FIG. 1b. However, in FIG. 2, instead of having justone carrier body, a carrier body 45 is divided into multiple separatecomponents or units, and each of the separate carrier units isimpregnated with the radioisotope 15. Each unit of the carrier body isused to concentrate, collect and support the radioisotope 15 and isdistributed substantially evenly along the length of the cavity 47. Inpreferred embodiments, each carrier body unit is constructed of the samematerial as the carrier body 20 in the previous embodiment and has asubstantially spherical shape like a bead or a ball so that each carrierbody unit can be easily rolled into the cavity 47, just like the X-raydetectable markers, to facilitate the manufacturing process. Thedimension of each carrier body unit and the number of the carrier bodyunits can be appropriately adjusted according to the dimension of thecavity 47 and according to the desired amount of radiation emitted bythe radioactive seed 30. However, as previously mentioned, the carrierbody units should be distributed evenly along the length of the cavity47 to ensure that the seed 30 emits substantially uniform radiationaround the housing 40 of the seed.

In addition to having multiple carrier body units, a multiple number ofX-ray detectable markers are distributed evenly among the carrier bodyunits to disclose the orientation and the location of the seed 30 whenthe seed 30 is exposed to X-ray photography. As shown in FIG. 2, theX-ray detectable markers 35 a and 35 c are disposed adjacent to the twoends 48 and 49 while the marker 35 b is disposed in the middle of thecavity 47. The number and the location of the X-ray markers should beadjusted appropriately depending on the circumstances, but there shouldbe at least two markers in the cavity 47 to allow for determination ofthe orientation of the seed 30, as discussed above.

FIGS. 3a-3 d show various different embodiments of the presentinvention. Each of the embodiments shown in FIGS. 3a to 3 d has a uniquearrangement of the carrier body 45 and the Xray detectable markers 35.FIG. 3a shows a radioactive seed smaller than the previous embodiments.The fourth embodiment shown in FIG. 3a has a single unit carrier bodywith two X-ray detectable markers. FIG. 3b shows a fifth embodiment of aradioactive seed in which the X-ray detectable markers are disposed inbetween the separate units of the carrier body instead of being placedat the two ends. This facilitates radiation being emitted by the end ofthe seeds. FIG. 3c shows a sixth embodiment in which there are two X-raydetectable markers and two carrier body units arranged in alternatingfashion. FIG. 3d shows a seventh embodiment of a radioactive seed inwhich the carrier body units are concentrated at one end of the seedinstead of being evenly distributed along the length of the innercavity. Such radioactive seeds can be useful in situations where theradiation has to be concentrated at certain points. Also, the X-raymarkers could serve to block radiation in one direction and helpminimize radiation effects on healthy tissue. In addition, because theX-ray detectable markers are disposed at the other end of the seed, oneend of the seed can be differentiated from the other end when the seedis exposed to X-ray photography.

FIG. 4 shows an eighth embodiment of the present invention. Aradioactive seed 60 shown in FIG. 4 has a housing 70, a cavity 67 andtwo ends 77 and 78 similar to the ones in the previous embodiments. Theseed 60 has a carrier body 65 comprised of multiple separate unitssimilar to the embodiment shown in FIG. 2, but the carrier body 65 maybe a single piece similar to the carrier body 20 shown in FIG. 1a. Incontrast to the previous embodiments, the seed 60 has an X-raydetectable marker 75 which wraps around the full length of the externalsurface of the housing 70 like a spiral or a cork screw. Since themarker 75 wraps around the full length of the housing 70, the marker 75will disclose the orientation of the seed 60 as well as its locationwhen the seed 60 is exposed to X-ray photography. However, the spiralmarker still permits radiation to be emitted through the spaces in thespiral or corkscrew. In alternative embodiments, the Xray detectablemarker 75 may be formed as an integral part of the housing or placed inthe interior of the cavity 67 so long as the X-ray detectable marker 75will not interfere with manufacturing or placement of the seed.

FIG. 5 shows a ninth embodiment of the present invention. A radioactiveseed 80 has a housing 81, a cavity 82 and two ends 87 and 88 similar tothe ones in the previous embodiments. However, the seed 80 has a singlecarrier body 90 disposed in the cavity 82 and an X-ray detectable marker85 which wraps around the full length of the carrier body 90 in a spiralshape. Since the marker 85 wraps around the full length of the carrierbody 90, the marker 85 will also disclose the orientation of the seed 80as well as its location when the seed 80 is exposed to X-rayphotography.

FIG. 6 shows a tenth embodiment of the present invention. A radioactiveseed 100 has a housing 102, a cavity 104 and two ends 108 and 109similar to the ones in the previous embodiments. The seed 100 also has acarrier body 110 comprised of multiple separate units similar to theembodiment shown in FIG. 2, but the carrier body 110 may be a singlepiece similar to the carrier body 20 shown in FIG. 1a. In contrast tothe previous embodiments, the seed 100 has X-ray detectable markers 105which have a substantially cylindrical shape with a hole through thelong axis of the X-ray detectable markers 105. The hole in the middleallows the radiation from the carrier body 110 to pass through themarkers 105 so that the ends 108 and 109 will also emit radiation. Inmany instances, the ends 108 and 109 tend to be thicker than other partsof the housing 102 since the ends have to be welded after the carrierbody 110 and the X-ray detectable markers 105 are inserted into thecavity 104. Consequently, less radiation may pass through the ends 108and 109. By having substantially cylindrical holes in the X-raydetectable markers 105, more radiation will be able to pass through theends 108 and 109 to alleviate the problem stated above. In furtherembodiments, the X-ray detectable markers 105 can also be modified suchthat the markers will be able to slide over a single piece carrier body.In other words, the carrier body can be inserted into the hole of themarkers so that the markers can be positioned over any part of thecarrier body.

FIGS. 7a through 7 d illustrate how different marker configurationswithin a radioactive seed can identify the type of radioactive sourcesin the seed and the dosage level of the seed. Each of the seeds 128,130, 132 and 134 include at least two radioactive markers 120 in aparticular configuration to identify the radioactive source in the seedand the dosage level. FIGS. 7a and 7 b show cross-sections of seeds 128and 130 having palladium-103 as a radioactive source in respective setsof carriers 122 and 124. Seed 128 includes three adjacent sphericalX-ray markers 120 a centered in the seed, leaving two radioactivecarriers 122 on each side of the three X-ray markers 120 a. In thisembodiment, this particular configuration identifies the seed 128 ashaving palladium-103 as the radioactive source at a dosage of about 0.3millicuries. Seed 130 has the same marker configuration of that of FIG.7a except that the center X-ray marker 120 a is replaced with a carrier124. This particular configuration also identifies the source aspalladium 103 but at a dosage of about 3.0 millicuries. The differentmarker configurations in seeds 128 and 130 are preferably detectable inX-ray imaging and allow the treating physician to distinguish theradioactive seeds implanted in the affected tissue region with the lowerdosage from those implanted seeds having the higher dosage.

The radioactive seeds 132 and 134 of FIGS. 7c and 7 d include respectivesets of carriers 126 and 136 for providing an iodine-125 radioacivesource. The radioactive seeds 132 and 134 also each include X-raymarkers 120 at each opposite end of the respective radioactive seed.With X-ray imaging, the treating physician can distinguish thoseimplanted radioactive seeds having radioactive markers at opposite endsof the seeds, corresponding with seeds having an iodine-125 source, fromthose seeds which do not have radioactive markers at opposite ends ofthe seeds, corresponding with seeds having a palladium-103 source. Also,in addition to having X-ray markers 120 c at opposite ends of thecapsule, the radioactive seed 132 also includes an X-ray marker 120 c inthe center of the capsule. The radioactive seed 134, on the other hand,does not include an X-ray marker in the center of the capsule. Thisallows the treating physician to distinguish implanted iodine-125 seedshaving dosages of 0.3 millicuries, with the X-ray marker in the centerof the capsule, from the implanted iodine-125 seeds having the 3.0millicurie dosage, with no X-ray marker in the center of the seed.

The embodiments illustrated in FIGS. 7a through 7 d enable the treatingphysician to better control and monitor the brachytherapy process in anaffected tissue area by using different types of isotopes (e.g.,iodine-125 or palladium-103) and using different levels of dosages inthe radioactive seeds. This allows the treating physician to properlydose the core and periphery areas of the affected tissue. For example, apotential problem in prostrate brachytherapy is the overdosing of thecore area with radiation and the under dosing of the periphery areas.The embodiments illustrated with reference to FIGS. 7a through 7 dpermit the accurate identification of the activity resulting from theimplanted seeds at both the core and periphery areas using X-ray imagingto maintain proper dosage levels in the affected areas.

Accordingly, the placement of markers within the seed can assist in notonly determining the orientation of seeds, but also differentiatingamong the different types of radioisotopes and levels of activity amongparticular implanted seeds. This is done by differentiating thedifferent types of radioactive seeds using different X-ray markerconfigurations which are detectable using X-ray imaging. It is in thismanner that the multiple markers in radioactive seeds as illustratedwith reference to FIGS. 7a through 7 d provide a previously unavailablesystem for monitoring the distribution of the activity of dosages in apatient's tissue during brachytherapy.

The radioactive seeds illustrated in FIGS. 7a through 7 d havingdifferent radioisotopes and dosages may also be manufactured using auniform manufacturing process. The process of manufacturing aradioactive seed for a particular radioisotope and a particular dosageis differentiated from the processes of the other types of radioactiveseeds by the selection of appropriate carrier elements for thecorresponding radio isotope and dosage level, and the placement of X-raymarkers among the selected carrier elements within the capsule. Thisenables a single manufacturer to cost effectively provide the differenttypes of radioactive seeds (i.e., having the particular radio isotopeand dosage level) which are distinguishable using X-ray photography.Moreover, the treatment clinic can purchase the different radioactiveseeds from a single vendor, simplifying a system employing differenttypes of radioactive seeds at different dosage levels and radioisotopetypes. This offers distinct advantages over such a systems which wouldrequire the purchase of radioactive seeds from multiple manufacturers toprovide differentiated radioactive seeds. With a system of seeds withmultiple markers from a single manufacturer, such as those shown inFIGS. 7a through 7 d, having X-ray detectable marker configurationsindicative of the activity level or isotope type, the inconvenience ofpurchasing from multiple vendors is avoided.

While the description above refers to particular embodiments of thepresent invention, it will be understood that many modifications may bemade without departing from the spirit thereof. The accompanying claimsare intended to cover such modifications as would fall within the truescope and spirit of the present invention.

The presently disclosed embodiments are therefore to be considered inall respects as illustrative and not restrictive, the scope of theinvention being indicated by the appended claims, rather than theforegoing description, and all changes which come within the meaning andrange of equivalency of the claims are therefore intended to be embracedtherein.

What is claimed is:
 1. A radioactive seed for use in radiation therapy,the radioactive seed comprising: a sealed housing having an internalcavity; at least one carrier body disposed within the cavity formaintaining a radioisotope, as a radiation source, in a distributionalong a length of the cavity; and a plurality of X-ray detectablemarkers distributed along the length of the cavity, at least two of theX-ray detectable markers being laterally separated from one another byat least one carrier body, wherein the distribution of the plurality ofX-ray markers reveals a seed treatment characteristic when the seed isexposed to an X-ray photography, said seed characteristic selected fromthe type of radioisotope maintained by the carrier body and the dosagelevel of the radioactive seed.
 2. A radioactive seed for use inradiation therapy, the radioactive seed comprising: a sealed containerhaving a cavity; a plurality of carriers substantially evenlydistributed and laterally spaced along the length of the cavity, each ofthe plurality of carriers containing and maintaining a radioisotope as aradiation source; and a plurality of X-ray detectable markersdistributed among the carriers such that the distribution of the markersdiscloses a seed treatment characteristic when the seed is exposed toX-ray photography, said seed treatment characteristic selected from thetype of radioisotope maintained by the carrier body and the dosage levelof the radioactive seed, wherein at least two of the X-ray detectablemarkers are laterally separated from one another by a carrier.
 3. Asystem for providing radiation treatment to an affected tissue area, thesystem comprising: a plurality of first radioactive seeds, each of thefirst radioactive seeds including: a sealed housing having an internalcavity; at least one carrier body disposed within the cavity formaintaining a radioisotope, as a radiation source, in a distributionalong a length of the cavity; and a plurality of X-ray detectablemarkers distributed along the length of the cavity, at least two of theX-ray detectable markers being laterally separated from one another byat least one carrier body, and an implantation device to position theradioactive seeds in the affected tissue area, wherein the distributionof the plurality of X-ray markers in each radioactive seed reveals aseed treatment characteristic when the tissue area is exposed to X-rayphotography, said seed treatment characteristic selected from the typeof radioisotope maintained by the carrier body and the dosage level ofthe radioactive seed.
 4. A radioactive seed for use in radiationtherapy, the radioactive seed comprising: a sealed housing having aninternal cavity; at least one carrier body disposed within the cavityfor maintaining a radioisotope as a radiation source; and a plurality ofX-ray detectable markers distributed within the cavity, wherein thedistribution of the plurality of X-ray markers reveals a seed treatmentcharacteristic when the seed is exposed to X-ray photography, said seedtreatment characteristic selected from a type of radioisotope maintainedby the carrier body and a dosage level of the radioactive seed.
 5. Asystem for providing radiation treatment to an affected tissue area, thesystem comprising: a plurality of radioactive seeds, each of theradioactive seeds including: a sealed housing having an internal cavity;at least one carrier body disposed within the cavity for maintaining aradioisotope as a radiation source; and a plurality of X-ray detectablemarkers distributed within the cavity, and an implantation device toposition the radioactive seeds in the affected tissue area, wherein thedistribution of the plurality of X-ray markers in each radioactive seedreveals a seed treatment characteristic when the tissue area is exposedto X-ray photography, said seed treatment characteristic selected from atype of radioisotope maintained by the carrier body and a dosage levelof the radioactive seed.